Safety device



Oct. 18, 1932. H. 5. WILSON ET AL SAFETY DEVICE 3 Sheets-Sheet 1 Filed May 15, 1926 llll 13, 1932 H. 5. WILSON ET AL 1,883,248

SAFETY DEVI CE Filed May 15, 1926 3 Sheets-Sheet 2 &

fllrzllguilllll Oct. 18, 1932. H. 5. WILSON ET AL SAFETY DEVICE s Sheet-Sheet 5 Filed May 15, 1926 Patented Oct. 18, 1932 UNITED STATES PATENT OFFICE HERBERT S. WILSON AND ADOLF E. FOHN, OF JULIET, ILLINOIS, ASSIGNORS, BY MESNE ASSIGNMENTS, TO MINNEAPOLIS-HONEYWELL REGULATOR. COMPANY, OF MINNE- APOLIS, MINNESOTA, A CORPORATION OF DELAWARE SAFETY DEVICE Application filed May 15, 1926. Serial No. 109,447.

The invention relates to safety devices- The employment of oil burners for the heating of houses, shops and similar buildings is constantly increasing because of the convenience connected with the elimination of the handling of coal and-the factthat o l burners are practically automatic in their operation. In order to render the employment of oil burners absolutely safe, the present invention deals with a device for shutting off the motor employed to drive the fuel pump and the air compressor which form essential parts of the oil burner system.

To this end a safety device is provided wherein a switch controlling the motor circuit is held in operative position by a thermostat influenced by the heat generated 1n the boiler, so that upon the failure of combustio'n after being established or ofsuiiicient heat being produced the motor circult is opened and no fuel is supplied to the combustion chamber nor does an ignition take place.

A further object aims at providing a safety device wherein the safety switch is normally held in position by an electrically controlled thermostat, and upon starting of the boiler system is held in position by a thermostat heated by the exhaust gases of the boiler, so that upon the failure of the boiler to operate, the safety switch is released and the motor and the ignition circuits are broken.

A still further object aims at providing a signal to indicate that the motor circuit has been opened.

With these and other numerous objects which will become apparent from a perusal of the description of the invention, the latter comprises the means described in the specification, particularly pointed out in the claims forming a part thereof, and illustrated in the accompanying drawings, in which:

Figure 1 is a side elevation of an oil burner system to which the invention has been applied;

Figure 2 is a front view of a thermostat;

Figure 3 is a cross section on the line 3-3 of Figure 4;

Figure 4 is a front view of a safety device;

Figure 5 is a similar view with parts arranged in different position;

Figure 6 is an enlarged section on the line 6-6 of Figure 4;

Figures 7, 8 and 9 are diagrams showing the circuits of the safety device, Fig. 7 showing the circuit conditions when the burner is not operating and when the room thermostat occupies the position indicated when the room temperature is normal, Fig. 8 showing the circuit conditions when the burner is operating and when the room thermostat occupies the position when the room temperature is below normal, and Fig. 9 showing the circuit conditions when the burner has ceased to operate but the room thermostat occupies the position when the room temperature still remains below normal.

Referring to the drawings and particularly to Figure 1, a boiler 10 of any standard or desired construction is provided with a stack 11 for the passage of exhaust gases. Spark electrodes 12 and 13 are connected through a step up transformer with a motor 15 which serves as a source of power for the actuation of an air compressor and oil pump (not shown) and. which are partof the oil burner system. Inasmuch as the present invention is not concerned with the oil burner system per se but deals only with the safety device used in connection therewith, reference is made only to those parts of the system which have any caring on the invention.

To the stack of the boiler a safety device generally designated by 16 is secured. This device comprises a casing 17 open at the front which ordinarily is closed by a cover plate 18. The back plate 19 is formed with a lug 20 to which a horizontally extending tube 21 is secured by a set screw 22. The tube 21 is provided with a flange 22 engaging the wall of the stack 11 and secured thereto by a plurality of bolts 23.

The tube has a slot 24: intermediate its ends and its free end is cut away as at 25 to form a lip 26 to which one end of a thermostatic coil 27 is secured. The other end of the coil is connected by a member 28 with the adjacent end of a horizontal rod 35 extending through the center of the tube 21 and through an aperture 29 in the lug 20. The rod extends into the casing 17 and the forward end has fast thereto a control member 30 bifurcated at the upper end to receive between the prongs a stop pin 31 and formed at the lower end with a tooth 32. A collar 33 is secured to the rod 35 and engages the back plate of the device casing 17. A spring 33a is interposed between the member 30 and collar 33. v

A mercury switch 34 is provided in the easing 17 and comprises a glass tube 36 having pairs of contacts 37, 38 and 39, 40 respectively at each end contacts 37, 38 belong to the motor circuit and contacts 39, 40 form a part of an alarm circuit as will be hereinafter further explained. The glass tube 36 is carried by a collar 41 which has an upper lug 42 and a lower lug 43. The upper lug is rotatably supported by a horizontal stud 44 of the back plate 19. Another horizontal stud 45 extends from the back, wall 19 below the stud 44 and receives a screw 46 to which is secured a member 47 having downwardly extending prongs 48 and 49. "Rea-rwardly of member 47 is a lifter member 50 which has upwardly extending an arm 51 and a finger 52 in engagement with the lug 43. The arm 51'may oscillate between stop pins 53 and 54.

A bimetallic strip 55 is secured at the bottom and its free end extends between the prongs 48 and 49. The strip is lined on the sides with mica plates 56 and a wire 57 constituting a heating coil is wound around the bimetallic strip but insulated therefrom by the mica plates. The wire continues and is wound into a resistance coil 58 adjacent to the mica strip. The resistances of the coils 57 and 58 are so proportioned relatively to each other that the heat developed by the coil 57,

wound upon the bimetallic strip 55, will not unduly stress the latter and thereby preclude its recovery to normal or unstressed position when it becomes cooled.

In addition to the safety device a thermostat or relay generally designated by 60 is employed which ordinarily is located in a. room.

This thermostat is of the usual and standard construction and for this reason no detail description of its parts is made except as necessary for an understanding of the presentinvention. As appears from Figure 2, the thermostat has similarly to the safety device, a mercury switch 61 being tiltably mounted and provided with two pairs of contacts for the motor and heater circuits respectively. A lever 62 controls the position of the switch, which in Figure 2 is in motor circuit closing position.

The operation of the oil burner system will be best understood by reference to the diagrams shown in Figures 79.

A short rsum of the circuit diagrams shown in Figs 7, 8 and 9 will now be presented. In Fig. 7, the circuit conditions are shown when the room temperature is normal or when the room thermostat 61 occupies hot position. The mercury switch 69 keeps the heating coil of the thermostatic actuator 55 normally energized through the circuit established between contacts 7 0 and 71, while the motor circuit is opened between the contacts 68 and 69. Since the thermostatic actuator 55 is normally heated the mercury switch 34 occupies such position that the mercury bridges contacts 37 and 38. F

In Fig. 8 the circuit conditions are shown which obtain when the room thermostat moves to cold position or when .the temperature of the room has fallen below normal. This requires operation of the motor M and the oil burner mechanism in order to raise the room temperature to normal. The room thermostat 60 thus moves to close the circuit between the contacts 68 and 69. The circuit is then interrupted between the contacts 70 and 71 whereupon the electrical heating ele ment of the thermostatic actuator 55 is disconnected from circuit. When the room thermostat .61 moves to establish a circuit between electrodes 68 and 69, the motor of the oil burner is energized and the oil burner now begins to function. Assumin that combustion is established by the oil burner, the stack thermostat 27 begins to heat up as the electrically heated thermostatic actuator 55 begins to cool. If combustion is established and maintained the stack thermostat 27 holds the mercury electric switch 34 in such position as to maintain the motor circuit through the electrodes 37 and 38. This is normal operating condition of the oil burner.

In the event that combustion has either not been established or has been discontinued after having been initiated the circuit conditions are then those shown in Fig. 9 wherein the room thermostat 6 occupies cold position as shown in Fig. 7 but the mercury switch 34 has moved to such position as to deenergize the motor circuit because the stack thermostat 27 has failed to hold the mercury switch 34 in the position shown in Fig. 7 after the thermostatic actuator 55 has lost is residual heat and also released its hold uponthe mercury switch 34. The conditions obtaining in Fig.9 illustrate the safety features of my present invention, namely, that the motor becomes deenergized when the stack switch fails to function properly. This is an abnormal operatin condition of the burner. Under this condition the alarm circuit is energized by reason of the circuit being established through the contacts 39 and 40 of the switch 34.

Referring to Fig. 7, the normal condition of my control circuit is illustrated therein, namely, the condition that obtains when the room temperature is normal and the motor M and the oil burner'are not in operation. Under these circumstances the room thermostat occupies hot position whereupon the heating element of the thermostatic actuator 55 is normally energized. In other words, the actuator 55 is electrically heated by the room thermostat when the temperature of the room is normal or above normal. In Fig. 8, the normal operating condition of the oil burner mechanism is shown. In Fig. 9 the abnormal operating condition of the oil burner mechanism is shown.

Figure 7 shows the arrangement of the various parts when the boiler. is shut down. Wires 65 and 66 lead to a source of electric energy such as a lamp socket in the ordinary household where 110 volt power is obtainable. A main switch 67 controls the connection't-o said source of energy. The mercury switch 61 of the room thermostat has the contacts 68, 69 for the motor circuits and the contacts 70 and 71 for the heating coil of the thermostat 55.

A wire 72 leads from the main switch to contacts 68 and 70, and a wire 73 connects the contacts 69, 37 and 39.

The contact is connected through a wire 74 with the primary. of a step down transformer whose secondary is short circuited through a bell signal 76. The heating coil for the thermostat is connected at one end through a wire 77 with the main wire 78 leading to the main switch 67 and at the other end a wire 79 leads to contact 71.

A wire 80 connects the contact 38 with one terminal of the motor M to whose other terminal the main wire 78 leads. In shunt with the motor is the primary of step up transformer 81 whose secondary is connected to the spark electrodes 12 and 13.

Figure 7 discloses the arrangement of parts when the boiler is shut down. If the main switch is closed current will flow through supply wire 65, main wire 72, contacts 70 and 71, through the heating coil of thermostat 55 and'back through the main wire 78 to the supply wire 66. No current will be supplied to the motor circuit as the mercury switch 61 is tilted to break the connection between contacts 68, 69, which are adapted to close the motor circuit.

When the boiler is to be operated the lever 62 of the room thermostat is set so that its mercury switch 61 is tilted with the left end pointing downwardly, as indicated diagrammatically in Figure 8.

Upon closing of the main switch 67, current will flow from the supply wire and. main wire 72, through the contacts 68 and 69, wire 73, contacts 37, 38, wire 80, motor'M and back through the main wire 78 to the negative pole of the main switch. At the same time the step up transformer 81 is energized and the spark electrodes 12, 13 will produce ignition of the atomized fuel supplied thereto.

No current will be supplied to the heating coil of the thermostat 55 as the circuit is broken through the contact and 71. The ther-' mostat 55 will then cool and straighten out (Fig. 4) and would permit the mercury switch 32 to tilt with the right end, as viewed in Figure 4, in lowermost position. However, before the thermostat 55 cools sufliciently to permit this end of the switch to drop the heat produced in the boiler stack affects the thermostat coil 27 which holds the control member 30 with its tooth 32 in engagement with the lug l2 preventing thereby the mercury switch from tilting with the right end downwardly. v

In case, however, the burner fails to operate properly and the heat generated in the stack is insuflicient, then as the thermostat 55 cools the switch 34 will actually tilt and occupy the position shown diagrammatically in Figure 9, in which both the heater circuit and the motor circuit are broken. In that event a current flows from wires 65, 7 2 to contacts 68, 69, wire 73, contact 39 and 40, wire 74, primary of transformer and back to main wire 78, energizing the transformer 75 and sounding the hell 7 6. By stopping the motor, of course, the accessory parts of the oil burner system are not driven, so that no fuel is delivered to the boiler and the danger of flooding is avoided.

Attention is called to the fact that in accordance with the present invention the circuit for the heating coil 55 is continuously closed-until the burner is set in operation, at which time the circuit is opened and the motor circuit closed. Thus, the room thermostatic-switch 61 operates alternately to either close the heater circuit or the motor circuit. If desired, the heater circuit may only be closed shortly before the burner is placed in operation and subsequently broken in order to complete the motor circuit.

From the foregoing description of our invention, it is obvious that the mechanism for operating the oil burner, which mechanism is subjected to control by the system and the safety switch of our present invention, comprises the motor M .whichis employed to drive the fuel pump and air compressor, as well as the ignition means for the oil burner which, as shown in the specific embodiment of our invention herein described, is connected in parallel relation to the motor M.

While I have explained the operation of our present safety switch in connection with a mechanism comprising a mercury electric switch, it is to be understood that our invention is not specifically limited to this type of electric switch except in those claims where in a mercury electric switch is specifically called for. The mercury electric switch, as defined herein, may be of many forms of con struction that are. well known in the art. The same comprises a sealed container which usually houses a body of mercury that details of arrangement of parts nor the particular electrical connections nor their specific construction, but claim our invention as broadly as the state of the art permits.

lVe claim: v

1. An electrical control circuit including switching means for the normal control of an automatic heating system, a safety switch normally held in a closed circuit position and in series with said switchingmeans, a bimetallic element forcontrolling said safety switch, means energized by electrical energy in said control circuit through the open circuiting of said switching means for actuating said bimetallic element to obtain a normally closed position through said safety switch, means responsive to heat conditions in said system for maintaining said safety switch in a normally closed position, and a resistance element connected in shunt across said safety switch.

2. in a control system for a fuel burning device comprising electrically controlled means for supplying a fuel mixture, the combination with a control thermostat, a thermostatically controlled actuator, an electrical heating element for said actuator the circuit of which is controlled by said control thermostat, of an electric switch adapted to be held in closed position by said actuator when the latter is heated, said electric switch controlling the operation of said fuel supply means when said control thermostat is closed, a safety control mechanism influ enced by the combustion conditions obtaining in the fuel burning device for controlling said electric switch and for causing said electric switch to remain in closed position as long as combustion continues but permitting said electric switch on the cooling of said actuator to move to open circuit position upon initial failure of combustion or of failure of combustion after being initiated, and means connected in shunt relation to said electric switch for precluding the operation of said fuel supply means when abnormal conditionsobtain in the congization thereof.

device comprising electrically controlled means for supplying a fuel mixture, the commostatically controlled actuator, an electrical heating element for said actuator the circuit of which is controlled by said control thermostat, of an electric switch adapted to be held in closed position by said actuator when the latter is heated, said electric switch controlling the operation of said fuel supply means when said control thermostat is closed, a safety control mechanism influenced by the combustion conditions obtaining in the fuel burning device for controlling said electric switch and for causing said electric switch to remain in closed position as long as combustion continues but permitting said electric switch on the cooling of said actuator to move to open circuit position upon initial failure of combustion or of failure of combustion after being initiated, and means for preventing complete deenergization of the control system when said electric switch occupies open circuit position.

4. In a control system for a fuel burnmeans for supplying a fuel mixture, the combination with a control thermostat, a thering device comprising electrically controlled bination with a control thermostat, a thermostatically controlled actuator, an electrical heating element for said actuator the circuit of which is controlled by said control thermostat, of an electric switch adapted to be held in closed position by said actuator when the latter is heated, said electric switch controlling the operation of said fuel supply means when said control thermostat is closed, a safety control mechanism influenced by the combustion conditions obtaining in the fuel burning device for controlling said electric switch and for causing said electric switch to remain in closed position as long as combustion continues but permitting said electric switch on the cooling of said actuator to move to open circuit position upon initial failure of combustion or of failure of combustion after being initiated, and means for preventing complete deencrgization of the control system when both said control thermostat and said electric switch occupy open circuit positions.

5. An electrical control circuit comprising switching means for the normal control of an automatic heating system, a safety switch normally held in closed circuit position and in circuit with said switching means, a member for actuating said safety switch into closed position, means responsive to the current flow in said control circuit and controlled by said switching means for controlling the operation of said actuating member, and thermal responsive means for maintaining said safety switch in a normally closed position.

6. An electrical control circuit including switching means for the normal control of an automatic heating system, a safety switch normally held in a closed circuit position, a member for actuating said safety switch into a normally closed position, means responsive to the current flow in said control circuit and controlled by said switching means for controlling said actuating member, means responsive to heat conditions in said system for maintaining said safety switch in a normally closed position, and additional means for preventing complete deenergization of said control circuit when both said switching means and said safety switch are in open circuit positions.

7. An electrical safety device comprising a mercury-electric switch biased to one position, a holder for-said switch, two separate thermostatic actuators for said switch disposed to be separately heated, and separate,

uni-directional connecting means between said actuators and said holder, each engage/ able with said holder to prevent said switch allowing said switch to move to the biased position of said supportin member, a second thermally actuated mem er separately engageable with said supporting member and when heated holding said switch in said position opposing the bias of said supporting member and when cooled allowing said switch to move to the said biased position.

in witness whereof we aiiix our signatures,

mRBERT S. WILSON. ADOLF E. FOHN.

from moving to its biased position but free to move out of engagement with said holder when the latter is engaged by the other or said connecting means.

8. An electrical safety device comprising a mercury-electric switch biased to one position, a holder for said switch, two separate thermostatic actuators for said switch, an electrical heating element for one of said actuators, means for supporting the other of said actuators in position to be influenced by an external temperature, and separate, uni-directional connecting means between said actuators and said holder, each engageable with said holder to prevent said switch from moving to its biased position but free to move out of engagement with said holder when the latter is engaged by the other of said connectingmeans. I

9. In an electrical safety device comprising a mercury-electric switch biased to one position, a holder for said switch, two separate thermostatic actuators for said switch, an electrical heating element for one of said actuators, means for supporting the other of said actuators in position to be influenced by an external temperature, and separate, unidirectional connecting means between said actuators and said holder, each engageable with said holder when the corresponding actuator is heated to prevent said switch from moving to its biased position but free to move out of engagement with said holder when the latter is engaged by the other of said connecting means. 10. An electrical safety device comprising an electric switch, a tiltably mounted biased member supporting said switch, a thermally actuated member engageable with said supporting member and when heated holding said switch in a position opposing the bias of said supporting member and when cooled 

